It is possible for a conventional audio reproduction device such as two-channel audio system, 5.1 channel audio system, etc, to move a sound image horizontally, but difficult to move it vertically and/or anteroposteriorly, because the system moves a sound image by changing each of amplitudes of acoustic waves from a plurality of loudspeakers arranged on the circle centering on a sound receiving point with an operation of a pan-pod on a mixing console.
Then, a device enabling to move a sound image three-dimensionally, that is, not only horizontally, but also vertically and/or anteroposteriorly has already been proposed. (See Patent Publication 1, Patent Publication 2 and Non-Patent Publication 1)
The device equipping FIR filters disclosed in Patent Publication 1 makes it possible to move a sound image not only horizontally but also vertically by using two loudspeakers arranged on the same horizontal plane.
The device disclosed in Patent Publication 2 makes it possible to move a sound image not only horizontally but also vertically by selecting loudspeakers generating an acoustic wave and controlling amplitude of the acoustic wave in accordance with the position (angle and distance) between a listener and the sound source.
Further, the device disclosed in Non-Patent Publication 1 makes it possible to form a sound image at the same position as a sound source by outputting acoustic waves whose amplitudes are determined based on the lengths of three vectors into which a position vector of the sound source from a sound receiving point is broken.
A panning device which makes it possible to pan a sound image when a plurality of loudspeakers are arranged along edges of a rectangular filed such as a theater has already been proposed. (See, Patent Publication 3 and Non-Patent Publication 2)
The device disclosed in Patent Publication 3 makes it possible to move a sound image by delaying an acoustic wave generated from one loudspeaker to another acoustic wave generated from another loudspeaker when a plurality of loudspeakers are arranged along edges of a rectangular filed such as the theater
Further, the device disclosed in Non-Patent Publication 2 moves a sound image three-dimensionally by applying a vector base amplitude panning method to a plurality of loudspeakers arranged three-dimensionally.    Patent Publication 1: Japanese Patent Publication No. 3177714 (See [001], FIG. 1)    Patent Publication 2: Japanese Unexamined Patent Publication (Kokai) No. H06-301390 (See [0010]-[0015], FIG. 1)    Patent Publication 3:U.S. unexamined Patent Publication No. 20020048380 (See [0026], FIG. 3)    Non-Patent Publication 1: “Localization of Amplitude-Panned Virtual Sources II: Two- and Three-Dimensional Panning” VILLE PULKKI, J. Audio Eng. Soc. Vol. 49, No. 9, 2001 September    Non-Patent Publication 1: “Virtual Sound Source Positioning Using Vector Base Amplitude Panning” VILLE PULKKI, J. Audio Eng. Soc. Vol. 45, No. 6, 1997 June